Transfer press



March 6, 1962 c. w. E. WALKER 3,023,805

TRANSFER'PRESS Filed Feb. 29, 1960 FgLZ ZZTZ/EZTZLUF Cb ar/e-s W5 Wd/Aer 5 7w w/wifgs.

United States Patent 07 3,023,805 TRANSFER PRESS Charles W. E. Walker,Beloit, Wis., assignor to Beloit The present invention relates broadlyto the art of paper making, and is more particularly concerned with anew and improved transfer press assembly and method of preventingcrushing at a transfer press nip, featuring the provision of a pressroll having a pattern of blind drilled holes therein effective asreservoirs to temporarily accommodate the press felt water content andthereby permitting an increase in nip pressures with the consequentimportant advantage of increased water removal from the paper web.

It is known in the art that at the couch roll end of a Fourdrinier papermachine the web is removed from the forming wire by a transfer orpick-up felt, which carries the web on the underside of the felt lowerrun to a first or transfer press, whereat the web is received by ortransferred to a press felt for water removal action by a subsequentpress section. It is further Within the knowledge of the art that thepaper web at the time of its advancement through the transfer press niphas a high water content and in fact may only contain from to 25% dryfiber, While the pick-up felt is also thoroughly wet with water in orderthat it may effectively remove the paper web from the forming wire andcarry the web to the transfer press.

It can accordingly be readily appreciated that, by reason of thegenerally saturated condition of the paper web and pick-up felt, the nippressures at the transfer press must be limited to a relatively lowvalue in order to avoid disturbances in fiber formation arising fromwhat is termed in the art as crushing. Specifically, when a high watercontent felt enters the transfer press nip and the pressures at said nipexceed a predetermined amount, there is noted to be at the oncoming sideof the nip a backward rush of water in opposition to the direction oftravel of the felt and web into and through the nip. This constitutes ahighly disturbing influence on proper fiber formation, and nip pressuresare therefore limited and little if any water is removed from the web atthe transfer press.

In addition, and notwithstanding the crushing problem, if the nippressures at the transfer press were suflicient to actually drive waterfrom the felt and through the web, any fines or loading materials in theweb are Washed out with the water and the desired sheet quality is notobtained. For this further reason, in the prior art the transfer presshas been limited to the sole function of transferring the web from thepick-up felt to a press felt, with essentially no water removal from theWeb at the transfer press.

It is accordingly an important aim of the present invention to provide atransfer press assembly of novel construction featuring avoidance of thecrushing problem and having the further important advantage ofpermitting increased nip pressures so that substantial volumes of watercan be removed from the web at the transfer press.

Another object of the invention lies in the provision of a method ofpreventing crushing in a high moisture content web traveling in contactwith a relatively wet felt, wherein the Web and felt are advanced towarda pair of relatively rotatable rolls one of which is provided with anarray of small diameter blind holes along the outer diameter thereof,said rolls rotated in nip-defining relation to advance said web and feltinto the nip and force the moisture in the felt into the holes in saidone of 3,023,805 Patented Mar. 6, 1962 the rolls, and the felt and webseparated at the off-running side of the nip while said rolls arecontinuously being rotated to release the moisture in said holes forreturn to the felt.

A further object of the instant invention is to provide an improvementin a press assembly having a pair of rolls in nip-defining relation andreceiving a relatively Wet felt and a high moisture content Web at saidnip, the improvement being principally directed to'the provision of aroll having on its outer diameter an array of relatively small diameterblind holes receiving moisture from the felt upon entry of said feltinto the nip, then holding said moisture therein during passage of thefelt through the nip, and next releasing said moisture to the felt uponits exit from the nip.

Other objects and advantages of the invention will become more apparentduring the course of the following description, particularly when takenin connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughoutthe same:

FIGURE 1 is a more or less diagrammatic representation of the couch rollend of a paper machine and embodying therein a transfer pressconstructed in accordance with the principles of this invention; and

FIGURE 2 is a detail sectional view of a press roll in the transferpress of this invention, to more fully illustrate the array ofrelatively small diameter blind holes therein.

Referring now to FIGURE 1, there is shown a paper machine generallydesignated by the numeral 10 and comprising a forming wire F looped overa suction couch roll 11 and a turning roll 12, the couch roll having asuction area 11a, and if desired, a saveall 13 in association therewith.The forming wire F supports a paper web W thereon over the couch roll 11and along a downwardly inclined wire run Fa.

The paper web W is removed from the downwardly inclined wire run Fa by alooped pick-up felt 14 which is urged against the Web W by a suctionpick-up roll 15 having a suction area 15a. The pick-up felt 14 is alsotrained around a plurality of guide rolls 16, a tensioning roll 17 and apress roll 18 of a transfer press assembly, generally designated at 19and to be later described in further detail. By action of the pick-upfelt 14 and suction pick-up roll 15 the paper Web W is carried along theunderside of lower run 14:: of the pick-up felt to the transfer pressassembly 19.

The transfer press 19 comprises, in addition to the top press roll 18, alower suction roll 20 having a suction area 20a, which in accordancewith this invention performs water removal functions in addition toeffecting transfer of the paper web W from the pick-up felt 14 to apress felt 21 at nip N defined by the top press roll 18 and lowersuction roll 20. Within the loop of the press felt 21 is a plurality ofguide rolls 22 and a tensioning roll 23, while outside of the loop areadditional guide rolls 24.

Downstream of the transfer or first press 19 is a second press 25 towhich the paper web W is directed and carried by the upper surface oftop run 21a of the press felt 21. The second press section 25 iscomprised of a top suction roll 26, having a suction area 26a, and alower press roll 27 within the loop of the press felt 21. The

roll 27 a suction press roll. A wide, variety of pick-up and'presssections are known to the art, and it will therefore be understood thatthe arrangement of FIGURE 1 is intended to be merely illustrative of anexemplary environment for the transfer press 19 of this invention.

In the conventional transfer press the pick-up felt wraps a press rollhaving an uninterrupted or solid outer diameter, whether it be providedby a rubber covered roll or a bare metal roll. Under the circumstances,when a substantially saturated pick-up felt and paper web of relativelylow dry fiber content enter the nip at the press and suction rolls ofthe transfer press, crushing in all reasonable likelihood will occur ifthe nip pressure exceeds a relatively low value. Crushing is of coursedestructive of good fiber formation, and it is therefore the customarypractice to apply at the transfer press only minimum nip pressure, andaccordingly, there is essentially no water removal accomplished from thepaper web at the transfer press. Further, and as was noted, the presenceof large volumes of water in the pick-up felt and the application of nippressures sufficient to drive through the paper web washes out fines orloading materials therein. This is of course additional to the problemof crushing, and the prior art has accordingly resorted to use of thetransfer press for the sole function of transferring the paper web fromthe pick-up felt to the press felt, and has accomplished essentially nowater removal at the transfer or first press. This necessitates the provision of a plurality of downstream press sections and a lengthening ofthe press end of the paper machine, in order to eflfect the desiredamount of water removal by the more economical mechanical expedient ofpressing, prior to transfer of the web or sheet to heated dryingsections.

In accordance with the novel concepts of this invention, the liquid orwater expelled from the pick-up felt by action of the nip is retained inthe press roll 18 of the transfer press during passage of the feltthrough the transfer press nip, so that at the nip a substantial amountof the water present in the paper web and in the lower press felt can beexpelled by the nip pressure and withdrawn through action of the suctionroll of the transfer press, since the excess pick-up felt water isessentially entirely and temporarily removed. Substantially higher nippressures can therefore be employed. By this invention crushing andwashing are essentially entirely eliminated, and by accomplishing webwater removal functions at the transfer nip, the efficiency of the papermaking process is markedly increased. As is known, at the nip N thepaper web W is transferred away from the wet felt 14 as they leave saidnip. Accordingly, rewetting of the felt 14 from the press roll 18 as itleaves the nip N does not also rewet the paper Web.

Apparatus effective to eliminate crushing and to produce the new resultsstated comprises the transfer press 19 and particularly a press roll 18constructed substantially in the manner shownin FIGURE 2. The press roll18, which is normally in the top position shown, is provided with aninner metal cylinder or shell 35 to which is bonded or otherwise securedalong the outer diameter thereof an elastomeric covering 36 having onlts-outer diameter a plurality of generally equally spaced and radiallyinwardly extending blind holes or pockets 37 of relatively short depthand relatively small diameter. in the exemplary embodiment of theinvention illustrated m FIGURE 2, the covering 36 is formed of rubber toprevent or reduce slippage of the pick-up felt 14 thereon, although thedesired degree of water retention could be accomplished if the blindholes 17 -were provided in a bare metal roll. However, a rubber covering36 has the further advantage of weight savings and ready replacement,and in accordance with this invention the covering 36 is of relativelylow deformability, having a hardness of about 30 PM, so that thecovering does not compress substantially at the nip to entrapsubstantial amounts of air therein, which would upon release of thedeforming or compressing force at the nip cause water in the holes 37 tobe spewed out by the entrapped air to create a possible disturbance toproper fiber formation in the Web traveling therebeneath.

The blind drilled holes 37 in the hard'rubber covering 36 are calculatedas to number, depth and diameter so as to accommodate at the nip N anappreciable amount of the total volume of water in the area of thepick-up felt 14 compacted at said nip. Illustratively stated, the holesor pockets 37 may have a depth ranging from A to about 1 inch, diametersranging from approximately to inch, and at a spacing to provide about10% to about 50% open area.

It will now be appreciated that when the top press roll rotates incounter-rotating relation with the lower suction roll 20, and the lowerrun 14a of the pick-up felt 14 in a highly wet condition advances andcarries the relatively low fiber content paper web W into the nip N, thewater or liquid in the pick-up felt is forced therefrom by the nippressure radially inwardly into the reservoirs provided by the blindholes 37 in the covering 36 on the top press roll 18. While the felt ispassing through the nip, the nip pressures prevent release of theretained water in said holes 37, and the water is not released forreturn to the pick-up felt 14 until the felt is at the offrunning sideof the nip and the nip pressures substantially reduced. The waterreservoirs provided by the holes 37 are thus effective to temporarilyremove from the nip N the water in the pick-up felt 14 to prevent theearlier noted crushing and washing conditions, and yet, sinceessentially the entire water volume retained in the holes 37 is releasedor returned to the felt at the off-running side of the nip, the pick-upfelt 14 is maintained at the desired degree of wetness for effective webpickup on the downwardly inclined wire run Fa. In other words, thepick-up felt 14 is returned to the web pick-up point generally definedby the suction area 15:: of the suction pick-up roll 15 at generally thesame moisture content as when the felt leaves the top press roll 18,although the normal water losses encountered in the absence of the toppress roll structure of this invention may necessitate replenishment andas well, conventional felt washing and wringing devices may be used onthe pickup felt 14 in the manner well known to the art.

Since by this invention there is temporarily removed from the pick-upfelt at the nip N the major volume of water in said felt, andaccordingly there is eliminated the problems of crushing and washingthrough the web at the nip N, the nip pressure at the transfer press nipcan be markedly increased so that the transfer press can now performwater removal functions on the paper web W. The nip pressure employedand the degree of water removal effected by the press felt 21 andsuction gland 20a of the lower suction roll 20 is of course calculatedto avoid any disruptions in fiber formation in the rela tively wet paperweb at the nip N, although by the novel transfer press 19 of thisinvention a substantial volume of web water is effectively removedwithout damage to the web, with the result that it is now possible toeliminate one or more downstream press sections and still provide apaper web which upon entry to the drying section is not in an abnormallywet condition. Accordingly, this invention has the important advantagesof eliminating crushing and washing which occurs when water is driventhrough the web, and now permitting water removal functions to beperformed at a transfer press, with the further advantageous resultsnoted.

An exemplary form of the invention has been herein described andillustrated in connection with a particular arrangement of pick-up andpress sections, although the invention is not so restricted and variouschanges and modifications may well be practiced without departing fromthe novel concepts of the instant invention.

I claim as my invention:

1. In a transfer press assembly having a pair of rolls in nip-definingrelation and receiving a relatively wet felt and a high moisture contentweb at said nip, the improvement which comprises a relatively hardelastomeric covering of low yieldability on one of said rolls and havingin its outer diameter an array of relatively small diameter radiallydirected blind holes receiving moisture from said left upon entry of thefelt into the nip, holding said moisture therein during passage of thefelt through the nip, and releasing said moisture to the felt upon itsexit from the nip.

2. A transfer press assembly, comprising a pick-up roll, a press roll, apick-up felt trained around said pick-up and press rolls, a suction rollin nip-defining relation with said press roll, and a press felt movablethrough said nip in contact with said suction roll, said press rollbeing provided with a relatively hard elastomeric covering of lowyieldability having on its outer diameter an array of relatively smalldiameter radially directed blind holes receiving moisture from thepick-up felt upon entry of the felt into the nip, holding said moisturetherein during passage of the felt through the nip, and releasing saidmoisture to the felt upon its exit from the nip, the suction roll andpress felt being effective to remove water from a traveling paper webduring passage through said nip and while the water from the pick-upfelt is retained in the blind holes in the press roll.

3. A press roll for use in a paper machine transfer press assembly andlocated in said assembly to be wrapped by a high water content felt,said roll comprising a generally cylindrical shell and a coveringthereon of relatively low deformability provided with an array of blindholes of a diameter and depth calculated to retain therein a substantialvolume of the water in said felt during application of nip pressure tosaid felt and to later release said water volume directly to the felt,whereby crushing at the oncoming side of the nip is avoided, the holeshaving depth ranging from one-quarter to about one inch, diameters fromone-sixteenth to one-quarter inch, and being spaced to provide from 10%to open area.

4. A method of preventing crushing in a high moisture content webtraveling in contact with a relatively wet felt in a transfer pressassembly, which comprises advancing said web and felt toward a pair ofrelatively rotatable rolls one of which is provided with a relativelyhard elastomeric covering of low yieldability having an array of smalldiameter radially directed blind holes along the outer diameter thereof,rotating said rolls in nipdefining relation to advance said web and feltinto the nip and force the moisture in the felt into the holes in thecovering on said one of the rolls without substantially deforming saidholes, and separating the felt and web at the off-running side of thenip while continu ously rotating said rolls to release the moisture insaid holes for return to the felt.

References Cited in the file of this patent UNITED STATES PATENTS1,880,686 Berry Oct. 4, 1932 1,938,444 Vedder Dec. 5, 1933 FOREIGNPATENTS 1,038,901 Germany Sept. 11, 1958 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,023,805 March 6, 1962 Charles W.E. Walker It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 5, line 11, for "left" read felt Signed and sealed this 19th dayof February 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents

